Our controls are not free (nor have they been) and you need to have a valid license to use them in production. You can reach out to our sales team at sales<at>telerik.com for further information on the matter, e.g. to get started with a trial account.
On using the 2011.1.315 version with SharePoint 2013 - it does not support it. It was created when SharePoint 2013 was not available and it is not likely that it can work with it. It does not support modern browsers (e.g., IE10, IE11, Chrome, Firefox) because it is 3,5 years old and they have had too many releases after that.
We advise using the latest version because it is the most advanced one available - with the most bug fixes and the most features.
In case you want to try using this old version in SP2013, you may find the following resources helpful:
I hope this explains the case.
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